package leetcode;
/*
* N形字符串
* */
public class Day6 {
    public String convert(String s, int numRows) {
        StringBuilder ret=new StringBuilder();
        int d=2*numRows-2;
        int n=s.length();
        if(numRows==1){
            return s;
        }
        //第一行
        for (int i=0;i<n;i+=d){
            ret.append(s.charAt(i));
        }
        //中间行
        for (int k=1;k<numRows-1;k++){
            for (int i=k, j=d-i;i<n||j<n;i+=d,j+=d){
                if(i<n) ret.append(s.charAt(i));
                if(j<n)  ret.append(s.charAt(j));
            }
        }
        //最后一行
        for (int i=numRows-1;i<n;i+=d){
            ret.append(s.charAt(i));
        }
        return ret.toString();
    }
}
